On Feb. 25, OpenAI signed a rental agreement to occupy approximately 439,000 square feet of office space at 350 and 380 Ellis St. in Mountain View, according to documents filed with the Santa Clara County Recorder’s Office. The deal will allow the artificial intelligence company to employ several hundred people and marks a significant expansion into Silicon Valley.
The move is seen as part of a broader trend of technology companies increasing their presence in the region. “This decision by OpenAI to make this big move will open the way for more AI companies to expand in Silicon Valley rather than in San Francisco (…) You definitely see tech companies take a bandwagon approach,” David Sandlin, executive vice president with Colliers International, said.
Newmark commercial real estate executives Phil Mahoney, Mike Saign and Jon Mackey represented the property owner in the transaction, while Newmark and JLL represented OpenAI. The offices at 350 Ellis St. total about 264,700 square feet and those at 380 Ellis St. total about 184,300 square feet. Each building is three stories tall.
OpenAI leased the buildings for ten years with options for two six-year extensions. The agreement also grants OpenAI a right of first refusal to purchase the buildings, though further details were not disclosed in public filings.
KKR Real Estate Finance Trust acquired ownership of the office hub through a deed in lieu of foreclosure posted in 2024. The foreclosure proceeding valued the property at $120.6 million, compared to $357.6 million paid by previous investors in 2021.
Recent data from Savills reported that full-year leasing volume for South Bay offices reached seven million square feet in 2025—the highest post-pandemic level—representing a 26% increase over 2024 figures. Sandlin said recent deals like OpenAI’s indicate that “office activity is definitely ramping up in Silicon Valley” and predicted continued improvement through 2027.
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